1. Field of the Invention
This invention relates to a driving device, and more particularly to a driving device for automatically exerting a variable torque on an output shaft, which rotates at a constant speed.
2. Description of the Related Art
Conventional driving devices include a power supply unit such as a motor, engine, etc., and a transmission unit, connected to the power supply unit to transmit power from the power supply unit to a load. The transmission unit may have a torque converter for changing a torque-speed ratio between an input shaft and an output shaft thereof.
A typical torque converter includes a gear train that can be operated by a gearshift, to output a variable torque that is required by a variable load. However, a problem with this conventional arrangement is that the user has to frequently manipulate the gearshift to ensure that a proper torque is exerted on the output shaft in response to the variable load. In addition, the rotational speed of the output shaft changes when the torque exerted on the output shaft is varied.
Accordingly, when the conventional driving device is used to drive a machine, such as an electric generator, etc., the operator must frequently adjust the power from the power supply unit to maintain the output shaft at a constant rotational speed, so as to allow the machine to work in a steady state. This causes an inconvenience to the operator.